1. Field of the Invention
The present invention relates to coin acceptors and, more specifically, to a coin detector for use in a coin acceptor, which uses spiral coils to measure the inductance value of the coin passing through accurately.
2. Description of the Related Art
Regular vending machines and game machines commonly have a coin acceptor, which uses a coin detector to detect the authenticity and value of inserted coins. A coin detector for this purpose according to the prior art design has an inductor element formed of a pot-like coil adapted to measure the inductance value of a coin. The inductor element may be made from iron, copper, nickel, aluminum, or lead. When electrically connected, the inductor element produces an oscillation frequency to induce the magnetic filed of any of a variety of coins. Subject to the coefficient of magnetism of the material of the coin detected, an eddy current is produced indicative of the intensity of the coefficient of magnetism of the coin. The inductance error of a pot-like coil is about 5˜10%. A pot-like coil tends to break, and tends to be interfered with ambient temperature. Further, a pot-like coil requires much installation space.